The present invention relates to a heterostructure field effect transistor for controlling the heterostructure field effect transistor having a current carrying channel layer composed of a semiconductor material having a high charge carrier mobility.
Such heterostructure field effect transistors are employed in analog high frequency circuits, for example, in monolithically integrated transmitter and receiver modules or in power amplifiers.
Publications by Saunier et al in IEEE Electron Device Letters, Vol. 9, No. 8, 1988, pages 397-398, and in IEEE Transactions on Electron Devices, Vol 36, No. 10, 1989, pages 2231-2234, disclose the incorporation of doping substances in the conductive channel of heterostructure field effect transistors (HFET) as homogeneous doping or in the form of a broad doping pulse. However, such doping worsens the transporting characteristics of the electrons in the HFET channel, that is, the mobility and drift velocity of the charge carriers becomes lower than in an undoped HFET.